Bioinspired Superhydrophobic Highly Transmissive Films for Optical Applications

Abstract

Inspired by the transparent hair layer on water plants Salvinia and Pistia, superhydrophobic flexible thin films, applicable as transparent coatings for optoelectronic devices, are introduced. Thin polymeric nanofur films are fabricated using a highly scalable hot pulling technique, in which heated sandblasted steel plates are used to create a dense layer of nano- and microhairs surrounding microcavities on a polymer surface. The superhydrophobic nanofur surface exhibits water contact angles of 166 ± 6°, sliding angles below 6°, and is self-cleaning against various contaminants. Additionally, subjecting thin nanofur to argon plasma reverses its surface wettability to hydrophilic and underwater superoleophobic. Thin nanofur films are transparent and demonstrate reflection values of less than 4% for wavelengths ranging from 300 to 800 nm when attached to a polymer substrate. Moreover, used as translucent self-standing film, the nanofur exhibits transmission values above 85% and high forward scattering. The potential of thin nanofur films for extracting substrate modes from organic light emitting diodes is tested and a relative increase of the luminous efficacy of above 10% is observed. Finally, thin nanofur is optically coupled to a multicrystalline silicon solar cell, resulting in a relative gain of 5.8% in photogenerated current compared to a bare photovoltaic device.

Adaptable bioinspired special wetting surface for multifunctional oil/water separation

“…2a495051. Hot pulling is a modified hot embossing process, in which demolding forces occurring during polymer and mold insert separation are used to fabricate high aspect ratio polymeric nano- and microstructures525354.…”

“…Subsequent mold retraction (0.3 mm/min) results in formation of dense nano- and microhairs. Samples used for oil/water filtration and hydrophobic recovery experiments were fabricated using a modified hot pulling technique in which initial PC films were attached to a sacrificial cyclo-olefin-copolymer layer51. Polymers used for nanofur fabrication include PC (Makrolon LED2045, Bayer, Germany); PLA (Uhde Inventa-Fischer GmbH, Germany); PET films (Hanita Coatings, Israel); PP, LDPE, HPDE films (Infiana, Germany).…”

Low‐Cost and Scaled‐Up Production of Fluorine‐Free, Substrate‐Independent, Large‐Area Superhydrophobic Coatings Based on Hydroxyapatite Nanowire Bundles

“…[28,29] Recently,s ilane and polymers were used to achieve high hydrophobicity.F or instance, Vüllers et al constructed nanohairs on polycarbonatef ilm by hot pulling. [30] Mates et al developed aw ater-based and fluorine-free superhydrophobic formulation by using environmentally safe constituents:T iO 2 NPs andp olyolefin copolymers. [31] The hydrolysis of silane and polymer, together with spray coating, also provideafluorinefree, substrate-independent, and mechanically durable strategy for superhydrophobic coatings.…”

Chemical and Physical Pathways for Fabricating Flexible Superamphiphobic Surfaces with High Transparency

“…Similarly, Vullers et al [104] reported a facile and efficient technique to produce superhydrophobic flexible thin films that are applicable as transparent coatings for optoelectronic devices. They fabricated a thin polymeric nanofur from optical-grade polycarbonate (PC) using a two-step fabrication process, comprised of hot embossing and hot pulling steps, as shown in Figure 11a,b.…”

“…With an aim on transparent, flexible, and self-cleaning properties, superhydrophobic surfaces have also been developed for eyeglasses and sunglasses. Possessing the properties of self-cleaning and optical transparency, a thin, flexible polymeric film could be applied for light management applications and it is attractive for commercial applications in optoelectronic devices [104]. Highly-flexible superhydrophobic thin film can be used for closed-end tubes and several uneven complex geometries [105].…”